The present invention relates to a method for informing the driver of a vehicle equipped with a combustion engine and an automatic start and stop system of the engine, that the unavailability of the automatic stop of the engine is a normal occurrence and no reason of concern for the driver. The information provided by implementation of the method is therefore reassuring for the driver.
Automatic start and stop systems of the combustion engine in vehicles are becoming more and more common. These systems, often designated by the acronym STT or by the English expression Stop & Start System, reduce fuel consumption and therefore polluting emissions, such as carbon dioxide emissions. In the text below, the term STT system applies to any automatic stop and start system of the combustion engine of a vehicle, which can be a hybrid type of vehicle or not.
The operation of vehicles equipped with an STT system requires two things: on the one hand, a request from the driver and, on the other hand, an authorization for the vehicle to enter into an automatic stop phase of the engine. Under certain constraints, (for instance low energy level of the vehicle, need for the powertrain group, need for protection or thermal regulation), the “vehicle system” can prohibit the automatic stop of the engine. The term “vehicle system” designates all of the normal control systems operating the elements of the vehicle, such as for instance the brakes, the engine, the transmission, the servo steering, the battery charge, the ABS and ESP safety systems. It involves therefore functional monitoring.
The operation of STT systems requires for instance sufficient means for restarting the combustion engine. If a battery is used to actuate the starter, the capacity and charge of the battery must be sufficient. One solution consists in increasing the capacity of the battery, but at the detriment of cost and occupied space. According to another solution, the battery charge is checked before every automatic stop of the engine in order to ensure that the battery charge is sufficient for the automatic restart of the engine. If this is not the case, the engine is not automatically stopped. However, this functionality can be misleading for the driver because he is expecting an engine stop under certain circumstances, for instance when stopping at a traffic light. In addition, some elements of the vehicles, such as the headlights, the radio or the climate control, consume electrical energy and, if the battery is insufficiently charged, the automatic restart of the engine could be problematic, or even impossible. It may be necessary then to prohibit the automatic stop of the engine, in order to maintain sufficient battery charge. This temporary unavailability of the automatic stop of the engine, unknown to the driver, can surprise and concern him.